In recent years, the brightness of a display device manufactured in a factory is adjusted in a brightness adjusting process of a manufacturing process. Particularly when the display device is a liquid crystal display device, the brightness is determined by output light of a backlight device that the liquid crystal display device has, and this output is adjusted.
For this brightness adjustment, a target value is set beforehand for every product of display devices. For example, for a certain product, when the outside air temperature is 25° C., a value of the brightness is set beforehand to 400±10 candela.
A brightness adjusting device used in such a brightness adjusting process measures the brightness of a display device, compares the measured brightness with the above target value, and adjusts the brightness of the display device such that the brightness of the display device becomes the target value. After the brightness is adjusted by such a brightness adjusting device, the display device is shipped as a product in a state where the target value is satisfied beforehand for every product.
In order for such a conventional brightness adjustment to guarantee a brightness value which is a target value, the brightness adjustment was performed after the determined warm-up time passed.
For example, the brightness was measured since 30 minutes as a warm-up time has passed after the power was supplied to the display device, and the brightness of the display device was adjusted.
In addition, the brightness of the display device changes not only with the warm-up time but also with the outside air temperature. For this reason, a technique of detecting a change in the outside air temperature and adjusting the brightness of a display device automatically based on the detected outside air temperature is known (for example, refer to Patent Document 1).
[Patent Document 1] Japanese Patent Unexamined Publication No. 11-2801